In general, a water meter is a device for measuring the amount of water supplied to a residential or commercial establishment from a water supply source. The amount of water used by the residential or commercial establishment is translated into a water bill issued to the residential or commercial establishment.
A water meter using a permanent magnet and a reed switch is used as a conventional water meter for measuring the amount of used water.
In detail, a meter using a reed switch is configured such that a permanent magnet is attached to a rotatable impeller and the reed switch is disposed outside the impeller. When the impeller and the permanent magnet rotate, the permanent magnet causes the reed switch to be selectively turned on or off. As the reed switch is turned on or off, electrical pulses are generated. The number of rotations of the impeller may be measured by counting the number of pulses.
The meter has a disadvantage in that since the reed switch operates due to a magnetic force, when an object having another magnetic force exists around the reed switch, the reed switch may not be smoothly turned on or off, thereby leading to an error in the pulses generated by the reed switch and failing to accurately measure a flow rate.